This study will determine differences in wear characteristics between self polymerizing and ultraviolet light polymerizing sealants, and between unfilled and filled sealants. The teeth used in the study will be unrestored, caries-free second molars and second bicuspids. A total of 60 subjects will be sealed initially, with one sealant type used in all four quadrants. Quantitative measurements will be obtained using silver copings made from immediate post-sealant tooth replica models. The amount of sealant applied will be determined by placing the pre-sealant die into immediate post sealant coping. A silicone-base impression material will be placed in the copings immediately prior to the placement of the dies, and a reproducible force will be applied on the die and coping. The volume of the sealant present will be calculated from the weight of the impression material between the die and the immediate pot-sealant coping using a micro-balance. At 1, 6, 12, and 24 month recall visits, full arch impressions will be taken and tooth replica models will be made. Post-sealant recall dies will be placed in the silver copings and sealant loss will be determined using the same procedure. Sealant loss will be reported as a percentage reduction in the volume initially applied to the occlusal surfaces. The data will be statistically evaluated by performing an analysis of variance with repeated measures in time. Scanning electron micrography will be done on a limited number of teeth after two years. Three teeth will be selected from each of the four treatment groups, and from each of three retention levels, sealant intact, sealant partially lost, and sealant clinically undetectable, for a total of 36 teeth. Profile changes will be assessed by sectioning the silver copings with the tooth replica models in place. Each half will be photographed on B/W sheet film, and tracings of the photographs from each half will be superimposed to give a picture of the wear profile throughout the two year study period.